1. Field of the Invention
The present invention relates generally to imaging devices and imaging methods, and more particularly to those permitting the capture of high resolution digital images of an original illuminated by light sources located outside of the optical field of view of an image sensor.
2. Description of the Related Art
Document copying devices are used in a variety of applications. These devices may be part of an all-in-one unit that includes scanning, printing, and facsimile functions. Alternatively, a document imaging device may be a stand-alone device, capable only of copying documents. Historically, imaging devices include a drive mechanism that moves a scan bar across a target document. In these devices, a document is scanned line-by-line, and the data downloaded to a processor. This data is combined to form a final two-dimensional image of the document. These imaging devices require precise movement of the scan bar to prevent registration defects. Accordingly, quality scans require intricate mechanisms which are often costly and complex.
Copying devices, whether of the all-in-one or independent variety, are popular for both business and personal use. Ideally, the devices are designed to have a size that enables placement within small workspaces such as desk tops and bookshelves. As a result, size is often an important aspect when deciding to purchase a imaging device. Other factors being equal, smaller devices are usually preferred because of their improved ability to fit where needed and to occupy a minimum space. Along with size, the price of the device is another important aspect during purchase. A device meeting other requirements may not be acceptable because of a higher price.
Digital photography technology has progressed so that image sensors that produce high-quality, two-dimensional images in a single capture step are now available. Image sensors including millions of sensor elements are readily available. These image sensors have also become more economical, allowing them to be utilized in new applications such as document imaging. An image sensor may have a substantial field of view, such that with appropriate placement within the imaging device the image sensor is able to capture most or all of a document original in a single image capture step. However, the relatively large field of view creates space and illumination complications. Improper placement of illumination sources may cause reflections that are manifested as reflection artifacts in the captured image. Placement of illumination sources to minimize reflection artifacts may in turn create difficulties in providing uniform illumination across the image target bed.
In addition to size and price, power consumption and component reliability are also important factors in consumer and business products. All of the preceding issues must be considered in designing a new imaging device.